The invention relates to a yarn conditioning plant for continuous processing of yarn, said yarn being drawn from a yarn supply, guided through a yarn processing chamber by a transport means, and then being wound on a spool.
The purpose of yarn conditioning plants is to condition yarn with the thread running continuously from spool to spool. This eliminates the need to make up the yarn into skeins for conditioning purposes, and then rewind the yarn. Therefore, the yarn conditioning plant is capable of performing various types of conditioning such as heat-setting unwrinkling, shrinking, texturing, steaming, drying, postforming or wet-treating various yarns in a continuous process. In addition, depending on the equipment in the yarn conditioning plant, several conditioning processes can be performed during a single pass.
According to one prior art conditioning plant (Hoerauf-Suessen GVA Yarn Conditioning Plant, Hoerauf Suessen Technical Information 6.3-00100E 9.75), in each of six working positions a mast carries four conveyor belts which extend through the yarn processing chamber. One or more yarn threads are continuously wound about the array of conveyors at one end, conveyed through the processing chamber to a temporary storage device formed at the other end of the conveyors, and then removed from the temporary storage device by a spooler, all as part of a continuous process.
Up until now this type yarn conditioning plant has been utilized with spoolers having only a single bobbin winder for each working position, i.e. whether one or multiple threads, simultaneously, were processed at a given working position, only a one single or multiple thread yarn was produced, as opposed to separation and individual winding of multiple threads that are simultaneously processed.
While it would be advantageous to be able to simultaneously process and separately wind a plurality of yarn threads in any one or more working stations, such has not been practical for several reasons. Firstly, prior art apparatus encounter problems with regard to separation of the yarn threads after processing, and furthermore, multi-thread systems would, at best, only allow the winding of so-called "cylindrical cheeses" (as opposed to cones ready for sale) which means an additional winding operation if cones are required.
It is believed that the above problems are directly related to the fact that the yarn threads undergo shrinkage during processing, which affects the length, bulk, and tension of the yarn. This problem is particularly acute with heat treatment processing for bulking carpet yarns which can cause up to an approximately 27% shortening of a processed yarn relative to its previous unprocessed condition. Since each yarn thread will not undergo the exact same changes, if a plurality of yarn threads are simultaneously processed on a common conveyor, even if only a 2% difference in shrinkage occurs, if a common drive is used to wind the finished yarn threads they will be under tensions which are different enough to result in one yarn thread being wound tight and the other loose in comparison. Such a difference in yarn tension is a problem since an optical streak will be present in a carpet that is then produced from such simultaneously processed yarns.
Accordingly, it is an object of the present invention to enable simultaneous processing of multiple yarn threads on single conveyance arrangements and separate winding of the individual yarns thereafter.
It is a further object of the present invention to provide an arrangement for compensating for differences in shrinkage so as to enable plural simultaneously processed yarn threads to be wound under substantially uniform tension.
These objects are achieved in accordance with a first preferred embodiment of the invention by providing an arrangement which detects the existence of a greater tension on one of the two processed yarn threads and effectuates a change of winding speed so as to equalize the winding tension on the yarn threads. In this first embodiment, a rocker-arm potentiometer produces a tension-differential proportional signal that produces the required winding speed adjustment.
Similarly, in a further embodiment independent temporary devices are provided for use with each of the separate yarn threads. The separate temporary storage devices enable the yarn threads to be placed in a condition of uniform tension and thus can be uniformly spooled by separate winding mechanisms.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention.